1. Field of the Invention
The invention relates to automatic stud welding devices wherein a headed stud is fed to a retaining collet on a gun, and more particularly, to a feed tube assembly which facilitates the removal of jammed studs from such devices and which provides additional safety features.
2. Description of the Prior Art
Various stud welding devices are known in which headed studs, commonly referred to as tee studs, are fed by pneumatic pressure to a collet or stud holding device which retains the stud for welding. Devices of this type are disclosed in U.S. Pat. Nos. 3,582,602, 3,597,573, 3,539,758, 4,263,888 and 4,284,870. In such devices, there is usually provided a metallic rod which is aligned with the collet and serves to force the stud into the collet and apply a force to the head of the stud during the welding operation.
For this reason, the stud must generally be fed into the conduit leading to the collet from a path which intersects the axis of the collet. It is therefore been found advantageous to feed the stud in a direction normal to the axis of the collet along a path which terminates in the circular bore or conduit, commonly referred to as the receiver, leading to the collet. It is generally at this point that jamming in the device will occur, if at all, due to the change in direction of the stud from a path perpendicular to the axis of the collet to a path normal to its axis.
Stud welding devices are now used on robot and machine tool applications, which means that continued operaton is necessary. The purity of the feeding of studs to the device must be continued. If there is a jam of the stud in the feeding passageway in the receiver, it must be cleared as soon as possible. When jamming occurred in prior art stud welding devices, it was generally necessary that the gun be taken out of service and a new one substituted for it, as the gun generally must be disassembled with appropriate tools in order to unjam the feedpath of the stud. This procedure is inappropriate for devices utilized in robot application.
One solution to the jamming problem is disclosed in U.S. Pat. No. 4,137,445. This patent describes a two part receiver block with one part being fixed and the other being pivotally attached to, or completely removable from, the first part. Jammed studs could be removed by pivoting or detaching the movable portion. This solution to the jamming problem, however, has not been completely satisfactory; first, because the two part receiver is costly to manufacture and second, because the device is covered and cased in such a way that time consuming disassembly must occur before the jam can be cleared. Moreover, this device does not address the safety problem of studs which are fed by compressed air shooting out of the feeding tube upon removal of a jammed stud or upon disconnection of the feeding tube.
It is therefor an object of the present invention to provide a stud welding device having a removable feed tube assembly which facilitates removal of jammed studs from the device. It is another object of the present invention to provide a stud welding device having, as a safety feature, the ability to prevent studs from shooting out of the feeding tube upon disconnection of the feeding tube, or when a jam has been cleared.